The invention relates to a process for carbonitriding metallic components, in particular steel parts. Specifically, the invention relates to a process for carbonitriding metallic components of fuel injection systems of air-compressing, auto-ignition internal combustion engines or of an air-compressing, auto-ignition internal combustion engine. Furthermore, the process is also suitable for transmission components.
DE 199 09 694 A1 discloses a process for carbonitriding in vacuum processes without plasma assistance. In the known process, molecular nitrogen is used as the donating gas, with a surface layer of a steel part being enriched with nitrogen at the end of the process. As the last step, a vacuum carburization process is followed by the carbonitriding step with nitrogen as the donor. The process pressure in this step is higher than the pressure in the carburization step. In this respect, the nitrogen donor can be added not only in the last process step, but also throughout the process.
The process known from DE 199 09 694 A1 has the disadvantage that, on account of the high carbon concentration which acts over relatively long times, carbides which can no longer dissolve during the further heat treatment can form in the base material. Depending on the loading, carbides close to the surface lead to premature component failure.